Refrigerators have been widely used to store objects to be kept fresh such as food or drugs at or below a predetermined temperature in households and in industry and commerce. A refrigerator includes a storage compartment to store objects and a cooling device configured to maintain the storage compartment at or below a predetermined temperature by supplying cool air into the storage compartment, allowing the objects in a chilled or frozen state at or below the predetermined temperature.
The storage compartment of the refrigerator may include a refrigerator compartment, a freezer compartment, and/or a temperature-variable compartment. The refrigerator compartment stores objects in a chilled state by maintaining the inside thereof at or below a predetermined temperature, and the freezer compartment stores objects in a frozen state by maintaining the inside thereof at or below a temperature lower than that of the refrigerator compartment. The temperature-variable compartment may store or preserve various types of objects at different temperatures in accordance with properties thereof by changing an internal temperature thereof in accordance with the types or properties of the objects.
A refrigerator may maintain the insides of a storage compartment at or below a predetermined temperature desired by a user by repeating evaporation and compression of a refrigerant. A refrigerator may include an evaporator, a compressor, a condenser, and an expansion valve to repeatedly perform evaporation and compression of the refrigerant.
In this case, a fixed speed compressor or an inverter compressor may be used as the compressor of the refrigerator. The fixed speed compressor refers to a compressor in which revolutions per minute (RPM) is fixed, and the inverter compressor refers to a compressor in which the RPM is variable. The fixed speed compressor sucks and compresses cool air at a constant RPM. The inverter compressor sucks and compresses cool air at a varying RPM.